Guidelines on superficial soft tissue tumors: should they be revised?

TL;DR

This study suggests that not all large soft tissue lumps need advanced imaging like MRI, as most are benign and can be safely treated with ultrasound and local excision.

Contribution

The study challenges current guidelines by showing that ultrasound is sufficient for many cases, reducing unnecessary MRI use.

Findings

99.8% of low-risk lesions <5cm were benign on histopathology.

Ultrasound had 95.3% sensitivity and 100% specificity for identifying lipomas.

Only 0.22% of low-risk lesions were malignant, and one was <5cm.

Abstract

Sarcomas guidelines suggest soft tissue lumps ≥ 5 cm, enlarging, painful or deep are considered malignant unless proven otherwise, should undergo a magnetic resonance imaging (MRI) scan and be referred to a specialist centre. Secondary hospitals receive multiple referrers from primary care for workup of subcutaneous, soft tissue lesions ≥ 5 cm with no other high-risk features. Strict adherence to recommendations can lead to overutilisation of limited resources.

We performed a single centre, retrospective cohort study at St John of God Midland Hospital in Western Australia, Perth on 552 patients investigated for subcutaneous, soft tissue lesions from 24 November 2015 to 30 September 2024.

83.5% (461/552) of lesions assessed to be overall low-risk were excised locally. 31.9% (147/461) had ≥ 1 high-risk clinical feature but none were atypical or malignant. Histological lipomas were the most common at 83.5% (385/461) followed by angiolipomas at 9.1% (42/461). 0.22% (1/461) lesion showed malignancy and was < 5 cm. Pre-operative ultrasound was most commonly utilised at 56.2% (259/461) with 95.3% sensitivity and 100% specificity for lipomas. MRI was the next most commonly used imaging at 19.1% (88/461). 16.5% (91/552) of lesions had radiological high-risk features. 54.9% (50/91) were managed at our state sarcoma unit. 84% (42/50) underwent excisions with 1 histological pleomorphic sarcoma which had typical clinical and imaging features of malignancy managed with wide excision.

99.8% (460/461) of patients with low-risk lesions <5cm were benign on histopathology. 50% (1/2) of subcutaneous, soft tissue lesions with malignancy were <5cm. Ultrasonography is highly sensitive (95.3%) and specific (100%) in characterising lipomas. This demonstrates that size alone should not be the sole indicator for escalation in investigation modalities (e.g. MRI), and that clinical assessment combined with ultrasonography is adequate in identifying low-risk lesions suitable for excision at non-sarcoma centres.

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